RE: [PATCH v2] i2c: designware: Do not complete i2c read without RX_FULL interrupt

Saha, Tamal
2021-12-14T13:06:50Z

Thanks Andy. I'll incorporate patch version changelog and review findings for this patch in next version.
Please let me know, if you have more findings for this patch.

> -----Original Message-----
> From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> Sent: Tuesday, 14 December, 2021 5:33 PM
> To: Saha, Tamal <tamal.saha@intel.com>
> Cc: wsa@kernel.org; jarkko.nikula@linux.intel.com; linux-
> i2c@vger.kernel.org; Senthil, Bala <bala.senthil@intel.com>
> Subject: Re: [PATCH v2] i2c: designware: Do not complete i2c read without
> RX_FULL interrupt
>
> On Tue, Dec 14, 2021 at 02:00:59PM +0200, Andy Shevchenko wrote:
> > On Tue, Dec 14, 2021 at 08:25:18AM +0530, tamal.saha@intel.com wrote:
> > > From: Tamal Saha <tamal.saha@intel.com>
> > >
> > > Intel Keem Bay platform supports multimaster operations over same
> > > i2c
>
> Here you put multimaster...
>
> > > bus using Synopsys i2c DesignWare IP. When multi masters initiate
> > > i2c
>
> ...and here multi masters.
>
> Be consistent.
>
> I believe the best way is to use dash variant, i.e. multi-master(s),
>
> > > operation simultaneously in a loop, SCL line is stucked low forever
> > > after few i2c operations. Following interrupt sequences are observed
> > > in:
> > > working case: TX_EMPTY, RX_FULL and STOP_DET
> > > non working case: TX_EMPTY, STOP_DET, RX_FULL.
> > >
> > > DW_apb_i2c stretches the SCL line when the TX FIFO is empty or when
> > > RX FIFO is full. The DW_apb_i2c master will continue to hold the SCL
> > > line LOW until RX FIFO is read.
> > >
> > > Linux kernel i2c DesignWare driver does not handle above non working
> > > sequence. TX_EMPTY, RX_FULL and STOP_DET routine execution are
> > > required in sequence although RX_FULL interrupt is raised after
> > > STOP_DET by hardware. Clear STOP_DET for the following conditions:
> > > (STOP_DET ,RX_FULL, rx_outstanding)
> > > Write Operation: (1, 0, 0)
> > > Read Operation:
> > > RX_FULL followed by STOP_DET: (0, 1, 1) -> (1, 0, 0)
> > > STOP_DET followed by RX_FULL: (1, 0, 1) -> (1, 1, 0)
> > > RX_FULL and STOP_DET together: (1, 1, 1)
> > >
> > > Signed-off-by: Tamal Saha <tamal.saha@intel.com>
> > > ---
> >
> > So, where is the changelog?
>
> --
> With Best Regards,
> Andy Shevchenko
>